Conventional electrochemical sensors generally include an electrochemical element which has an electrochemical pump cell with a preferably flat first solid electrolyte body and first and second preferably porous electrodes. These conventional sensors further include an electrochemical sensor cell which interacts with the pump cell and has a preferably flat second solid electrolyte body and a third and a fourth preferably porous electrode. The electrochemical sensor also has a gas inlet opening and a gas inlet duct, which is connected at one end to a measured gas chamber. The other end of the gas inlet duct opens into a cavity, also referred to as a gas chamber, lying inside the electrochemical element. The second and third electrodes and preferably one diffusion resistor arrangement are located in the gas chamber. The diffusion resistor arrangement can be formed by a porous filling. The measured gas enters the cavity via the gas inlet opening and the gas inlet duct, with the first and second electrodes of the pump cell regulating the entry of the measured gas into the gas chamber. This produces a controlled partial pressure of the gas component to be measured. The electrochemical potential difference between the electrodes of the second solid electrolyte body (which is due to the different partial pressures of the gas in the diffusion resistor arrangement and in a reference gas chamber located, for example, in the second solid electrolyte body) can be detected by a detecting device, such as a voltmeter unit, positioned outside the electrochemical element.
Conventional electrochemical sensors are also used in applications such as catalytic emission control in internal combustion engines under. These electromechanical sensors are designated in the industry as "flat broadband lambda sensors".
One of the disadvantages of the conventional electrochemical sensors is that they demonstrate elevated ripple during a lambda=1 pass, especially at high operating temperatures. This leads to problems, especially in control processes where the lambda value represents the controlled variable. Due to the ripple in the lambda signal, it is sometimes not possible to set an adequately stable output quantity.